[Milsurplus] APN-1 and ARN-1

[J. Forster]

Just as a point of interest,  the main difference between the Army and Navy
variants of this system seems to be that the Navy version (ARN-1)  is single range
( 0 to 400 ft) and the Army version (APN-1) is dual range (0 to 400 ft &  0 to
4000 ft).

-John